Sprags and similar devices are often used to transfer rotary movement from a drive member, e.g., an inner race, and a reaction member, e.g., an outer race in a first direction, e.g., clockwise, and to not transfer rotary movement therebetween in a second direction opposite the first direction, e.g., counter-clockwise. Typically a sprag includes a partially arcuate outer surface that is biased into frictional engagement with an inclined surface associated with either or both of an outer surface of the inner race and/or an inner surface of the outer race. Upon movement of the drive member in the biasing direction, the sprag becomes wedged between and substantially locks the drive and reaction members together. Upon movement of the drive member in the non-biasing direction, the sprag overcomes the biasing force, moves away from the inclined surface, and establishes sliding contact between the drive and reaction members. Thus, when the sprag substantially locks the drive and reaction members together, torque applied to the drive member is transferred to the reaction member, and when the sprag establishes sliding contact between the drive and reaction members, torque applied to the drive member is not transferred to the reaction member.
U.S. Pat. No. 5,482,144 (“the '144 patent”) issued to Vranish discloses a three dimensional roller locking sprag. The sprag of the '144 patent includes two pairs of curved peripheral side surfaces which respectively contact a pair of mutual diverging side wall surfaces of a groove disposed within a drive member and a reaction member. The sprag of the '144 patent substantially locks the drive and reaction members together for torque transfer therebetween in a first direction and establishes a sliding contact therebetween in a second direction.
Although the sprag of the '144 patent may transfer torque from the drive member to the reaction member in a first direction, movement of the drive member is required to lock and thus transfer torque to the reaction member. Additionally, the sprag of the '144 patent passively transfers torque from the drive member to the reaction member. Furthermore, the frictional engagement of the sprag of the '144 patent in a substantially locked position may be insufficiently small to transfer relatively large torques between the drive and reaction members.
The present disclosure is directed to overcoming one or more of the shortcomings set forth above.